One hundred percent of the campus electricity will now come from a 19-acre solar-energy system approved by Eversource late last month.

Half the system at Hampshire had been operating since June.

According to a press release, campus officials believe this is the first residential college in the United States to have this designation.

Butte College, a community college located about 75 miles north of Sacramento, California, went all solar in 2011.

At Hampshire, the 15,000 photovoltaic-panel arrays on two fields have a capacity of 4.7 DC megawatts -- which means 3,000 metric tons of greenhouse-gas emissions will be eliminated a year. That is equivalent to taking almost 650 cars off the road, and enough to power about 530 homes, the college said.

The project is part of the college's Climate Action Plan and Sustainability Initiative.

That initiative includes rooftop solar arrays on its R.W. Kern Center, the CSA Barn, the president's house, and the canopy atop the Chuck and Polly Longsworth Arts Center.

Relying on solar power will also cut costs.

The college is buying the electricity at a fixed rate from SolarCity, which built and owns the system, for about half the rate the college had been paying, according to college officials.

The project is estimated to save the college about $400,000 a year in electricity costs for up to 20 years, for total estimated savings of $8 million.

The college has been planning how to generate all of its electricity from renewable sources since 2014. In 2015 the board of trustees approved a plan for the construction of the array on campus.